Chapter 9. Regulation of Transcription from the lac Operon of E. coli

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Animation Activity: 9-4: Regulation of Transcription from the lac Operon of E. coli

1.

The ________ is responsible for the binding of the lac repressor to inhibit transcription from the lac operon.

CAP site

promoter

operator

lacZ gene

cAMP

Correct.

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2.

Maximal transcription occurs from the lac operon:

in the absence of both glucose and lactose.

in the presence of glucose and the absence of lactose.

in the absence of glucose and the presence of lactose.

in the presence of both glucose and lactose.

when the lac repressor is bound to the operators of the lac operon.

Correct.

Incorrect.

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3.

In the presence of both glucose and lactose:

RNA polymerase is bound to the lac operon.

the lac repressor is bound to the operator.

the lacZ gene is transcribed at high levels.

cAMP is bound to the CAP site of the lac operon.

The lacZ gene is not transcribed.

Correct.

Incorrect.

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4.

If E. coli cells are grown in the lab in growth medium containing both glucose and lactose and then switched to medium containing only lactose, what molecular change would you expect to occur at the lac operon?

The repressor would bind to the operators.

RNA polymerase would bind to the lac operon.

lacZ transcription would no longer occur.

cAMP would bind to the CAP site of the lac operon.

No change is expected because E. coli cells preferentially metabolize lactose.

Correct.

Incorrect.

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Chapter 9. Regulation of Transcription from the lac Operon of E. coli

Introduction

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